This application claims the benefit of German patent application DEP10040108.2 filed Aug. 17, 2000, herein incorporated by reference.
The present invention relates to a creel for a textile cheese-producing machine and, more particularly, to such a creel which comprises an integrated electromotor drive device which can be loaded or charged with a braking current counter to the nominal rated current of the electromotor for braking the cheese.
Such creels are known, e.g., in conjunction with bobbin winding devices that were developed for the production of cheeses of the xe2x80x9cprecision windingxe2x80x9d and xe2x80x9cstepped precision windingxe2x80x9d types.
Subsequently published German Patent Publication DE 199 08 093.3, for example, describes a bobbin winding device in which a cheese held in a creel is directly driven by a drive motor integrated into the creel. The cheese rests on a pressure roller that is not driven itself. Traversing of the yarn to be wound takes place by means of a finger-like yarn guide operated by a separate drive. The two drives can be controlled via an appropriate control device such that a defined, pre-selectable winding ratio is always obtained.
Since it is necessary to stop a cheese frequently in the course of the overall process of winding yarn onto the cheese, for example, when a yarn supply cop is exhausted, upon a yarn break, or following a controlled cutting of the yarn via a yarn cleaner, the known winding device also comprises a pneumatically loadable braking device integrated into the creel. This known braking device is comprised of a brake lining fixed on the stator housing of the electromotor to rotate in unison with the housing, against which brake lining a contact surface of a tube receiving plate, embodied as a brake disk, can be pneumatically pressed. The braking force thereby produced rapidly brings the cheese to a stop.
However, this known cheese winding device has a number of disadvantages. Both the rotating brake disk and the stationary brake lining are subject to significant wear and therefore the braking device requires intensive maintenance. In addition, the brake dust created can readily enter into the axial sliding guide of the cheese drive as well as into the bearing of the electromotor and considerably hampers or may even cause breakdown of these components.
Other cheese winding devices are known, for example from German Patent Publication DE 198 36 701 A1, in which a grooved drum that drives the cheese and at the same time traverses the yarn is electrically braked to a standstill after the cheese has been lifted off. To this end, the drive motor of the grooved drum is loaded or charged with a braking current that is usually a multiple of the rated current of the drive motor. In the process, the drive motors of such cheese winding devices are subjected to considerable loads, especially when large cheeses must be repeatedly braked and accelerated at short time intervals. Thus, such drives are exposed to significant stresses, especially thermal loads.
It is known from German Patent Publications DE 21 06 898 A1 or German Patent DD 214,114 that textile machine drive devices which are subjected to large thermal loads can be provided with cooling ribs so that the motor heat can be removed via convection and radiation into the ambient environment. Alternatively, as described in German Patent DE
27 14 299 C2, such drive devices can be cooled by a permanent application of compressed air.
These known drive devices are comparatively large, bulky and heavy, especially when correspondingly large output data are demanded. However, drive devices which are intended to be integrated directly into the creel of a cheese-producing textile machine must be as small and lightweight as possible, since during the winding process their weight results in an additional unwanted load on the rotation of the cheese on the associated pressure roller, especially when such a drive device is arranged far to the front on the creel. Thus, these known drive devices are only very poorly suited for being integrated in the creel of a textile cheese-producing machine. Therefore, such drive devices arranged in the area of the tube receiving plates of a creel should be as lightweight as possible but nevertheless strong in performance. However, the achievable power strength of an electromotor, e.g., of an electronically commuted direct-current motor is considerably dependent on the magnitude of its removable heat flow.
In view of the previously described state of the art, the present invention therefore seeks to address the problem of overcoming the disadvantages of the devices known in the state of the art and, more particularly, the present invention seeks to develop a creel that makes it possible to use relatively small and therewith lighter weight drive devices with great power density while assuring a sufficiently great strength of the drive devices.
The present invention addresses this problem by providing a creel of the type basically comprising an electromotor drive device integrated into the creel, wherein the creel may be braked when necessary by loading the electromotor with a braking current which initiates a braking moment directed counter to a rated current of the electromotor. In accordance with the present invention, a coolant circuit is arranged inside the creel for removal of motor heat from the electromotor.
The design of the creel in accordance with the invention has the particular advantage that the motor heat produced by the electromotor is immediately distributed onto a relatively large cooling surface. This assures that a thermal overloading of relatively small drive devices is prevented, even when they are fully loaded, and safety cutoffs due to overheated drives, that result in losses of efficiency of the textile machines, are avoided.
In a preferred embodiment, the coolant circuit comprises a heat receiving extent in the area of the electromotor and a cooling extent that is distinctly longer in comparison to the heat receiving extent. The cooling extent is formed to extend either within one of two creel arms or within the complete creel. In both instances, the creel wall located in the area of the cooling extent acts as a heat exchanger so that a large part of the motor heat produced can be removed over a large surface area and thereby dissipated into the environment.
The coolant circuit is preferably embodied as a closed system, i.e., the coolant circulates within the system without direct contact with the environment. Either a liquid, preferably water, or a gas, preferably air, may be used as coolant.
In an advantageous embodiment, the circulation of the coolant takes place via free convection wherein the change of density of the coolant occurring due to the heating of the coolant in the area of the heat receiving extent causes the coolant to flow inside the cooling circuit and thereby transports the introduced motor heat from the heat receiving extent to the cooling extent where the heat is removed via the creel wall into the environment.
In an alternative embodiment, the transport of heat within the coolant circuit may be supported by forced convection. In this instance, depending upon the type of the coolant used, either a ventilator or a liquid pump is arranged inside the coolant circuit. The use of such an additional, external power source can increase the circulation of the coolant inside the coolant circuit and therewith improve the cooling performance of the device.
It is also possible to design the coolant circuit as a partially-closed circuit, wherein compressed air is constantly or temporarily blown via an injector nozzle into the coolant circuit and the circulation of the coolant supported therewith. Excess compressed air is removed thereby through an appropriate air evacuation bore.
Further details, features and advantages of the present invention will be described in and understood from an exemplary embodiment described hereinbelow with reference to the accompanying drawings.